1. Warm up the engine to operating temperature, with the battery fully charged. Unscrew the spark plugs.
2. Remove the connectors from the fuel injectors of the fuel injection system.
3. Install a compression gauge into the spark plug hole of the first cylinder.
4. The assistant should press the accelerator pedal all the way down and turn the engine over with the starter. After turning the crankshaft one or two revolutions, the compression pressure should increase to the maximum and then stabilize. Record the maximum result obtained.
5. Check the remaining cylinders in the same way.
6. The compression pressure in all cylinders should not differ by more than two units. Note that the compression value should increase quickly on a healthy engine; low compression pressure on the first revolution of the crankshaft, followed by a gradual increase in pressure on subsequent revolutions of the crankshaft, indicates wear of the piston rings. Low pressure on the first revolution of the crankshaft, which increases slightly thereafter, indicates loose valves, a broken cylinder head gasket, or a crack in the cylinder head. Worn valve stem ends can also cause low compression pressure.
7. Peugeot does not specify the exact compression pressure, but if the compression pressure in the cylinders is less than 10, this indicates engine wear.
8. If the pressure in one cylinder is low, then perform the following test. Pour some engine oil into the cylinder through the spark plug hole and check the compression pressure.
9. If pouring oil into the cylinder increases the compression pressure, this indicates that the cylinder or piston rings are worn.
10. Low pressure in two adjacent cylinders indicates a burnt-out gasket between the cylinders.
11. If the pressure in one cylinder is 20% less than in the others and the engine runs rough at idle, this indicates a worn camshaft lobe.
12. If the compression pressure is too high, this indicates that the combustion chamber is covered with a thick layer of carbon deposits.
13. After this check, screw in the spark plugs and connect the high-voltage wires to them.